The proposed research involves the exploration of the hypothesis that regulation of phaseotoxin (the toxin produced by Pseudomonas phaseolicola) by resistant tissues of Phaseolus vulgaris, is the basis of their resistance to P. phaseolicola. The structure of phaseotoxin A has been determined and confirmed by chemical synthesis. The structures of the remaining phaseotoxins (B, C, D) will be determined by C13 and proton n.m.r. spectroscopy and IR and Mass Spectrometry. Synthesis of phaseotoxins in a cell free system will be undertaken using standard biochemical procedures and a study of regulation of synthesis of phaseotoxin will be made. The previously reported relationship between the inhibition of ornithine carbamoyltransferase of Phaseolus vulgaris by phaseotoxin and the production of chlorosis will be further investigated. Phaseotoxin suppresses the hypersensitive reaction and accumulation of antibacterial compounds of resistant tissues which are normally produced in such tissues when they are inoculated with the pathogen. The mechanism of this suppression will be studied. Finally, attempts to isolate compounds from resistant host tissues which suppress toxin synthesis by pathogen will be made.